1. Field of the Invention
The invention relates to a solid-state element device in which a phosphor-absorbs a light radiated by a light-emitting diode (hereinafter referred to as “an LED”) element and wavelength-converts the light thus absorbed into a light having a different wavelength to radiate the resulting light, and a light-emitting apparatus using the same.
2. Description of the Related Art
With regard to a light-emitting apparatus in which a phosphor wavelength-converts a light radiated from an LED element to radiate the resulting light, for example, a light-emitting apparatus is known in which after a phosphor solution is made to adhere like a thin film to a surface of a glass sheet through screen printing, another glass sheet is stacked up on that glass sheet and the thin film-like phosphor is thermally fused to form a wavelength converting portion, and the resulting wavelength converting portion is sealed on a lead frame having an LED element installed thereon, so that a light resistance property and a uniform wavelength conversion property are obtained. This light-emitting apparatus, for example, is disclosed in JP-A-2005-11953.
However, when the glass sealing construction is adopted, the conventional light-emitting apparatus involves the following problems.
(1) The phosphor is not uniformly dispersed into the glass since a viscosity of the glass is high at a sealing temperature or so (at about 600° C.).
(2) In order to reduce the viscosity of the glass until the phosphor is uniformly dispersed into the glass, a high temperature of 900° C. or more is required. However, at such a high temperature, there is encountered such a problem that not only the electrodes of the LED element cannot withstand the sealing processing, but also the phosphor and the glass chemically react with each other.
(3) When a glass having such a viscosity that the phosphor is uniformly dispersed into the glass even at a low temperature is used as a sealing material, since a differential thermal expansion between a ceramic base and the LED element is generally large, cracks occur in the glass, and thus the satisfactory glass sealing cannot be performed.